Dude, right now we have four completely different screen sizes (iPad mini, iPad, iPhone 4/4S, iPhone 5/5C/5S) and three different aspect ratios (iPad, iPhone 4/4S, iPhone 5/5C/5S) and yet it hardly has an impact on the quality of applications. Developers could handle even more, and you know why? Because there is HUGE money in it.
And we have the 90's coming back to bite Apple on the ass. Too many SKUs and screen sizes. Sure Apple has the billions in the bank now to absorb this mess, but it is a worrying trend.