If you're asking HP to dole out money and throw bodies toward rebuilding outreach efforts to bring back old and bring in new webOS developer talent, they aren't going to do it at this time, and especially not for anything 3.0.5 and prior.
Nor are they going to re-hire the editorial, writing, and design teams for Pivot.
Nor are they going to spend the money to complete HP Play as it was meant to be.
Nor are they going to extend the App Catalog internationally.
On that last point, it takes money to get accounting (taxes!) and legal representation (red tape!) to expand to different countries; right now they're already supporting what amounts to a catalog on life support, and don't you think they'd have done this long ago already if they ever intended to? If anything, were it ever in the plans to begin with--and it likely was to an extent, I imagine--they were almost surely cancelled when HP threw down the axe on devices.
There's simply no reasonable way for HP to justify blowing a bunch of money opening up the App Catalog to serve the two people in Turkey who managed to purchase a Pre off eBay for a few bucks, and that's where RumoredNow and Remy X's idea of a third-party App Catalog really makes sense since they're small and don't have 6 miles of red tape they need to work through...unlike a publicly-traded multinational corporation that isn't allowed to play cowboy. Irony, huh? But it's the truth.
Palm and HP also did "Appathons" paying out nearly a couple million bucks in the past. Guess what? Many quick and hastily-thrown together apps were released as a result, and many actually won cash despite the poor quality--even above some fantastic and well-thought out apps. Many who won also cut and run after getting the cash (just like BB devs will with the $10k "guarantee"), and others invested it into expanding to other platforms given that the webOS developer base was already shallow and picking up little to no steam even then. If you've been around here long enough, you know that those "Hot Apps" Appathons came during a very slow time between the Palm Pre/Plus and Pre 2 when things were looking...desperate for the platform under Palm. Which is why the PDK "Hot Apps" was done by HP right after they bought Palm out--and they lowered the prize values, to boot.
Oh, conventions. Open webOS already visits industry conventions, but there's no point to them working to attracting app developer talent if there's no complete OS yet to actually develop for; it's still an OS in development and it would be pointless to do so. (And how many legacy webOS apps break in Open webOS, again?) At least give them enough time to stabilize the platform and produce the next iteration of the SDK before wondering where the developers will come from.
And conventions may be good on a face-to-face basis, but 99.9% of the success of a platform is going to come from developers talking to other developers about their awesome development experience and money they're raking in rather than how they were convinced at a conference to come on board. Look back at the old webOS developer conventions Palm/HP used to have, and tell me how much that helped overall. Not much other than brand exposure; it's not by any means the crucial factor in platform selection by a developer. (Google I/O, Apple's yearly shindig, and Microsoft's conventions attract existing developers and those who are already true believers, so they don't count. Apples to oranges.)
The problem goes back to something very fundamental that the Blue Sky Echo Chamber here seems to be forgetting: There is no retail presence for webOS. Legacy webOS is dead. The number of active webOS users grows smaller by the day. The incentive to create webOS apps as a means of revenue is non-existent. Open webOS isn't even out in the open yet in a completed state and, as such, can't be profited upon by app developers. Just as or even more importantly, there are no announced devices on the roadmap for Open webOS--and rumor is not an announcement.
Look at Astraware's total sales over more than a year; a good deal of comparable apps sell that in less than a day on other platforms. Your average Joe Developer out there already looks at the #3 and #4 platforms, Windows Phone and Blackberry like they're a joke until the developer community decides to latch on en masse (if they ever do); webOS as a reasonable platform to release on, to them, has been long dead and buried. And developers, as a general rule, don't do charity cases for lone OSes when they need much more to financially support themselves.
Furthermore, when it comes to the donation idea to attract developers, it's been mentioned several dozen times around here but not one person who's mentioned it has actually done anything to create an actual plan and organize such an effort. Much less get it up and running. In, again, almost a year and a half now. They talk up the idea, then whine about why nobody else is doing anything about it.
tl;dr: These ideas are largely the same unrealistic ones talked about ad nauseum around here, and as usual they're predicated on HP beating dead horses by burying and asphyxiating them with currency.