Well they did decide to show the progression from Phase I clone armour to Stormtrooper armour so it's safe to say someone in Lucas film was paying attention then, so it's possible someone will with Boba and his appearance (of-course they also showed they weren't paying attention in the Special Edition's with things like getting the shoulderbells the wrong way around so they may screw it up completely!)
As to boba taking his helmet off and some of the mystery remaining, we already know what he looks like, or will look like (to a degree) when he gets to Jango's age. We know where he's from and what happened to him during his formative years so what mystery is there that the TV show could destroy? Another thing is that very few actors will want to remain faceless with a helmet on when they are the star (or co-star) of the show. In the films it worked because we weren't seeing much of Boba, but when we got to see Jango we had to see his face in order to see him as more then just a faceless killer. We needed to connect to him and that's nigh on impossible if you don't know what he looks like under the helmet.
Look at Hollywood for examples: Judge Dredd - Stallone takes his helmet off (much to the chagrin of fans). Robocop - Takes his helmet off, hell! Even the predators take their masks off! And tv shows do it more then films. As far as I can see there is no reason for Boba not to take his helmet off, at least in this coming series.