I went on the 5th and you have my exact opinion.
I marathoned Sheikra and I love it, but y'know...it's a dive coaster. Tigris is thrilling, but doesn't scratch much of a itch for me. Kumba is good but losing its luster for me. Same with Montu. I'm honestly not a big fan of positive Gs and inversions (Kumba's zero g roll still slaps, but it's the only part of the ride I really care for these days). Cheetah Hunt is just fun, but nothing to write home about (and screw the ridiculous wait times). Cobra's Curse was a perfect addition to me. IG will also be a perfect addition as well as the Screaming Swing.
If certain parks can have multiple B&M airtime machines, then the SWC can have two separate ones at two separate parks, and I agree a single rail is basically the only other addition that would turn heads if not some crazy Intamin that seems unlikely when Uni gave us that already (and they already have a multi launch).
The Giga feels like the only thing they might actually be able to squeeze in unless they're going to get rid of something or raze festival field for the single rail (and even then probably just a clone of the basic model).
Ultimately, the lineup is starting to feel stale. Obviously IG will solve this for the foreseeable future, but I couldn't help but look to the future.
The GP must feel this way too. I can't remember the last time I waited more than a train or two for Kumba and the Montu isn't much better. I know they're capacity monsters, but still.