29ers for tall people:
I agree a tall person looks more in proportion on a 29er but that's now how you should pick a bike?
I've rode big bikes and smaller bikes and it's a completely different riding experience. Both great but small does everything big does, but it doesn't work the other way.
Do you use the same pressures
Tall people can be thin and small people can be fat so could easily weigh the same.
bar width and grips as a 5 footer?
I'm well over 6' and run 750 wide bars. A lot of smaller folk run similar width (i don't get the grip thing)
I'd make 650 the standard and be done with it. They make money and we, when we decide to change, get a slightly better* bike.
If you love you're 26, don't fret. Keep it. Plenty of retro bikes about. 26 can be neo retro. Parts? Of course but you'll not be riding it all the time so the lack of choice wont be an issue. Special Sundays when the suns a shining.
Same for 29. Except they'll be show ponies - novelty bikes that get the very occasional ride when friends are round everyone's tipsy.
*650b is, on paper, slightly more suited to what a mountain bike might be required to do for most people. This is reinforced somewhat by what riders are saying. I can't think of the disadvantages of a slightly bigger wheel. Except money, and you don't have to buy until you are ready and happy to.