Can OS 4 succeed by having two major killer apps (MS Office and Adobe's Creative Suite [maybe just Photoshop]) ported?
No. A lack of quality applications can hurt sales, but having those applications won't spur sales.
I already have Photoshop and Office on cheap, powerful, and plentiful hardware. What do I need them on expensive, underpowered, and low volume hardware for?
And that's not to mention that there is no way you'd get these things, anyhow. Heck, Firefox has taken how many years, so far? It's far simplier than either of those, and we have the source code to it!
The only way a 'killer app' approach that might work is to come up with something no one has done before and no one realized they were missing until they see it. And even then, it would only take about 2 days from the first time a linux user sees it until there is then a Linux clone of it underway.