key word: problems, which I agree with. I'm not suggesting simply removing the black bar will turn the company around. I also wouldn't say that if they do keep it the M10 won't be successful. I'm simply saying that they've used the design 3 years straight, and people expect a more significant design change this year.
I'm sure you saw @evleaks render from last year. the HTC logo was on the bottom bezel, no black bar, and people on this site were drooling over it. 90% of us, myself included, were disappointed and didn't end up buying it. was that the only reason? of course not. the camera (which IMO is underrated) was also a major issue. the M10 will be about camera quality, aesthetics, software and the features (fingerprint sensor, USB-C, etc) we all expect in 2016. most importantly, like you said, it'll be about marketing.
Personally I'd love to see a nice sized battery (3400+ mAh) with a 5.7" display. I'd also like if they offer a compact version for the people that prefer a smaller screen. Force touch would really get my attention though. I'm hoping either the M10 or S7 has it but we'll see. I have a 6p but need a new work phone, so USB-C will be a strong consideration for me. I'd hate to have to use two different chargers for everything. In fact, I'd get another 6p before I bought a device without it.
The way I see it, it doesn't matter if the people on this site are drooling over it. In order to save HTC, it's up to the masses.
(And my rebuttal if someone brings up that posters on this site can influence the masses enough to be significant, the Nexus would be a top seller and we all know that it's not)