Both must stay if Juve has any ambitions.
Financially, Juve are in the red for the 1st time in 7 years but the problem has been forthcoming for a while. It points down to deeper, more fundamental financial problems (why did you think Moggi re-negotiated to performance-based wages?), doesn't it? Hence, what makes anyone think that selling our best players will rectify the financial problem for more than a season? As a PLC, I'd think that the money acquired will be used to offset the existing losses, NOT purchasing new players ... not unless anyone wants to go the 'bubbly' way like Lazio and Roma to appear bigger than they actually are. Nobody in their right minds pisses off their shareholders/investors and there aren't many better ways to do so than unjustified spending.
Footballing-wise, again, what makes anybody think we can replace players in the category of Nedved and Trez instantly? Young talents are good and all but for the fact that they usually take a few seasons to blossom. Meanwhile, what do we do? Isn't this wasting the 'peak' time of our current core men? I hardly think babysitting them in critical positions such as Nedved's and Trez's is such a good idea. In any case, I doubt that the same people clamouring for such changes will have the patience to see them out before screaming for the same thing again in 6mths. Where does that leave us then? The best part of prospects (or something which you cannot get) is that they appear extremely interesting but reality's quite another thing. Juve is very much in touch with the latter.
Personally, I think our attackers have done wonderfully well individually in a flawed collective system.
Basically, if they aren't the problem, they shouldn't be made to shoulder it all.