I wouldn't hold your breath on a "fix" as it's usually a contact issue inside the mixer and needs disassembly to cure, but yes Quadcabby's correct it can normally be fixed but if you're not happy opening the box, find someone who is!
As to future upgrades etc I was talking to a guy at Andertons here in the UK, who have the the M20ds on offer at £699.00. He reckons when they're gone there are no more coming to the UK. When you look at Yamahas TF series and how close the presets and general screen similarity is to the M20d, I think it unlikely he was spinning me a line. Why would Yamaha have a company they own, and to whose technology they already have access, spend money on R&D and creation of a product that could potentially rival their own line of mixing desks, at a lower price point?
The QSC Touchmix 30 seems a good bet as a reliable alternative at the right money, and with more flexibility re auxs etc. Time will tell I guess. There's been no official announcement and I think the Line 6 Link will be relegated to guitar related products, if kept at all.