Well, from Ferrari's release about the F430's airbag issue :
"In its petition, Ferrari details its plans to continue the F430 line until late 2008, when it will "be replaced by a newly designed eight-cylinder model." "
Note that Ferrari did not mention the new V8 model as the F430's replacement/successor. I believe that that "newly designed eight-cylinder model" is to be the new front-engined GT (commonly referred as Dino).
Imho, this opens the possibility that the F430's spiritual successor (mid-engined) could have an engine that is not necessarily a V8. Could be a V10 or even a small displacement, very high-revving V12 derived from the 599/Enzo (as once rumored a while ago).
With the new front-engined V8 as the new entry level Ferrari (making it in a way IS the F430's successor), and that the new mid-engined car will move up a class in price, I don't see why Ferrari would still be offering a V8 (making it sound like entry-level).
As for the V8's association with F1, well, since engine development is practically frozen for 4 years ahead, I don't see the need to spend money to keep developing the V8. Personally, for displacements of 5-litre and above, I would rather see a 'small' V10/V12 than a 'large' V8 not unlike AMG's 6.2L V8.
The MY 2008 Gallardo will have a 550 bhp, 5.2L V10 with direct injection (FSI), and its successor will have even more power, so Imho Ferrari should really investigate the possibility of offering at least a V10 for their next generation mid-engined model, which by the time it comes out will see the Gallardo's successor already only a year or two away from launch.
Please note that this is just an opinion...one might agree or disagree.