That's what it looks like, and it's not merely a shadowing by Oda, it is very clearly laid out that Yami and Hito are required to beat IMU...this means the last battle is either of the 2 below:
1. Luffy + Blackbeard vs IMU
2. Luffy vs Blackbeard - 1, Luffy gets seriously injured
3. Shanks vs. Blackbeard
4. Shanks dies
5. Luffy vs Blackbeard - 2, Luffy kills Blackbeard in rage over killing shanks
