They won't get rid of metro, it will evolve. I expect it'll be more like win7 was to vista. Minor tweaks and people loved it. Why, a lot of it was down to the almost three year timescale, for two reasons, people got use to it and drivers where released. that was the biggest issue. With win8 people aren't use to it and the app store was tiny and pretty rubbish except for a few stand out apps, the app store has always improved massively and by the time win9 rolls out should be looking good.
What would be nice is horizontal splits as well as the current vertical splits. Slight change in scaling for large monitors. And even better support for multi monitor. Being able to pin stat screen to one screen permanently for example.
How on earth can you put a percentage do it, have you looked at steam stats recently.
People mistake metro doom and gloom with pc doom and gloom.
People simply aren't upgrading as much as they were and those that do upgrade are generally buying ios/android devices. Corporations on the other hand always have huge lead times before implementing anything new.
Do you honestly believe they are just going to close down their app store, admit defeat and roll over and die?
As that's what you and others are saying you want to happen, with out a modern o's to compete in the mobile market that is what will happen. We've already seen massive companies replacing existing infrastructure with tablets, especially for mobile staff.
Even if win9 is loved, don't expect great pc sales. It'll be a continues decline of conventional pcs until it hits a certain level, where it will level off. mainly due to corporations still needing conventional pcs. Many homes no longer need or have desktops and rely on laptops and now even that is starting to change in favour of smartphones, tablets. Most people do not need huge cutting edge computers anymore, they just need a bit of document work and the rest is media consumption.