Firstly bbPress and TalkPress are explicitly different things.

It was an unfortunate mistake IMHO to name the hosted WordPress solution WordPress.com, a large portion of people just don't see or understand the difference between WordPress.com and WordPress.org and support questions get sent the wrong way for both.

It is good to see the seperation in branding between install it yourself (bbPress) and hosted (TalkPress).

While I agree is is good practise to try and get all the relevant domains for your brand there are other issues at stake here too.

The bbPress name fits well into the *Press family.