I have plans for 5 more, but I'll probably think of at least 3 more than that over time. Right now, I have plans for:

1. 2 follow up pics to the Sonic/Rainbow Dash series

2. 1 follow up pic for the racist/masochist Pinkie Pie series

3. An Applejack/Twilight/Tails pic

4. A Big the Cat/Derpy Hooves pic