Mos proceeds well.
Devs will obviously choose the best when the time will come.
I think the best is actually still x64-x86: Cheap warhorse, expandable by a kid, easy to assemble as your main computer and as easy to change it with a new one in your mainstream computer shop. What other hw platform can give mos better days?
You can choose a restricted hw platform Too and decide it to be the target mos machine with a Little internal hw market to be born.
Arm is a nice niche, but one thing is to buy the latest smartphone with its totally working stuff, another thing is to buy a pandaboard (or similar ware) on an internet only shop with hobbist micro boxes and to try to develop for it with a very Limited documentation. That is wonderful if you have a good dose of smoke to sell. But mos isn't smoke: Mos has good potential. Let's think pro.
Obviously this is only my p.o.v.. :)