Apple will probably never go down, but it will for sure lose some customers.
Those people that once enjoyed the Mac platform for its semplicity, and all they cared about was not the Mac Appstore/iTunes, nor even useless expensive speedbumps or the Facetime HD, will simply get bored and start look elsewhere for other options.
I don't know about you. But to me, it was a different thing paying $2500 for a "17 Macbook Pro back in 2007 then now. At least i knew that for 3 yrs or so, i had a performant machine that won't had become obsolete in a year.
Changing my Mac workstation every year, to have the ThunderBolt or the latest "Made in Cupertino" feature is not my cup of tea, sorry.
I would still say it is better than the Windows PC alternative. Been there, and will never do that again. My C2D 2009 27" iMac (my first Mac) is still going strong. Its the best performing desktop I have owned. Then again that's not saying much when all I have to compare against are the Windows PC's of my past.