No, it won't. It's a lot easier to write something meant to be open than to open something meant to be closed. And I'm cautiously optimistic that that's exactly the path they're following -- Maemo 5 is certainly more open than the previous versions, and Meego is definitely shaping up to be more open yet. Given the relative difficulty of running old OSes on new hardware (if only because nobody cares to make it happen), I'd rather have a modern computer with a fully-open platform layer 2 years from now, than have a fully-open (even including applications) Maemo 5 at the same time, and be stuck running it on my N900.
And what does Nokia get, in return for this huge effort and expense, to open old closed-source components? A measure of community goodwill, from the community surrounding the old device. So opening Diablo would greatly boost Nokia's trust with all the people who won't buy the N900 because they don't want a phone/are married to an incompatible carrier/are presbyopic and need a larger screen, as well as with the old guard who did upgrade. Much less (although still some) effect for people who got in at step 4. I suppose they may feel some moral relief about no longer providing bugfixes, but corporations don't run on morals. All in all, making Meego more open seems to have much better ROI.
And I'm cautiously optimistic that that's exactly the path they're following -- Maemo 5 is certainly more open than the previous versions, and Meego is definitely shaping up to be more open yet. Given the relative difficulty of running old OSes on new hardware (if only because nobody cares to make it happen), I'd rather have a modern computer with a fully-open platform layer 2 years from now, than have a fully-open (even including applications) Maemo 5 at the same time, and be stuck running it on my N900.