I think DTW220 would be the most likely candidate for the next base.

It's going to be flying out of DTW by then (if it hasn't already started) and in addition to that, it seems like the initial signs of 717 drawdown from non-ATL bases have appeared. Something will fill that void but that's more of 2-5 year plan I'd imagine.

But, if the 717s might be gone in five years, then they'll certainly be relegated to ATL-only just as the 88s are, perhaps only 3-5 years from now.