So is the end really just a reboot of the whole series but with a new God? Or is there any chance of a continuation. Because I'd really like to see how the series would differ without Ushimitsu around.
Uh-huh, I'd totally agree. Though, if you ask me, I think that would've made a great plot twist at the end of original series instead. Imagine, Akashi getting to the end and wanting to kill the God that made everyone suffer so much... only to discover that "God" himself went through the exact same process! And he was actually a close comrade of his, trying to make things better! That would've been a brilliant, completely unexpected way to end the series.
So while I do agree that continuation would be very much welcome, in my opinion, Ushimitsu should've been the God of the main series to begin with. He would've been so much more interesting than some unmotivated, randomly-chosen God like Kamimaru.