I think this is the right move for the show. They've already played all of their big cards that they've been setting up for so long and last season's ending seems to be almost the "point of no escape" for the main characters. There's really only one big card left to play and that's EVERYONE finding out Dexter's secret, which is probably happening sooner than later.
I'm glad they stuck to their guns and are committed to ending the show this season. There are rumours that, since last year's ratings were so good, they'd extend Dexter another season but I'd bet that the ratings bump was due to people turning in BECAUSE it was the second-last season and they wanted to see the endgame.
Last season was uneven but generally good and a major improvement over the terrible sixth season. Let's hope S8 can be even better.
"It breaks your heart. It is designed to break your heart. The game begins in the spring, when everything else begins again, and it blossoms in the summer, filling the afternoons and evenings, and then as soon as the chill rains come, it stops and leaves you to face the fall alone." --- Bart Giamatti, on baseball