Should healers now be allowed to play how they choose to play?

[Spiroglyph]

You're allowed to stick to your own playstyle - if that's healing ONLY, well, go right ahead.
However keep in mind that it's NOT against the TOS to kick people for different playstyles though, so if you're ever in a team that feels you should indeed be contributing to DPS, they can kick you and GMs are unlikely to do anything about it (unless of course they harass you, but then they'd get in trouble for another matter entirely).
Optimizing your job/role and utilizing all skills available to you is, to some players, something that is considered fun (personally I see healer DPS as utility - some DPS have team wide buffs, SMN rez, BRD/MCH regenerate TP/MP, so on so on, and healers can dish out some DPS to minimize time spent in an instance), and something that makes your contribution to the team's performance that much higher - now, I'm not going to argue with you why you should or shouldn't DPS; strictly speaking as a healer your core purpose is to keep the team alive long enough to see the instance cleared.

Wether or not the "healers need to DPS" mindset will remain or not will depend mainly on
1) Healing reqs for SB fights
2) Wether CS is or not one of the skills SE decides to remove

Bottom line, if nothing changes and instances (and their difficulty level) and skills remain unchanged, you CAN only heal, if that's what you want to do - keep in mind that people are not obligated to like that, and they're well within their right to kick you.