Capped, Yes please. But ... we don't really know what exactly is coming up and what these dungeons will be like nor what SE intends them to have for a function. If these dungeons are meant to replace part of the SP we gain through leves, cap would be kinda pointless... as already suggested by prior posts maybe level sync in that case ?
I voted for capped because I remember how much fun I used to have running through capped missions, BCNM, COP and mostly because of how boring COP got once it was uncapped. This is of course a personal preference which may change once the update is out and we discover that SE has had a totally different idea of what the function of Toto-Rak and Dzemael should be ...