The 7D being a flagship?
Why spend so much time on sticking a label on these products?
The 7D is just what it is, with exactly the features that it has! Discussing the "flagship" or "pro" labels doesn't help anybody because it's completely irrelevant, it's not as if the camera changes because it gets assigned an arbitrary label.
Let's at least speculate about the constellation of the product line-up, or about specifications of non-existing cameras, anything is more interesting than these labels!
To go on a journey you have to have directions. Directions are useless unless you know where you are.
So whether the 7D is indeed a flagship product is important and it will detirmine the marketing direction of its replacement
from a marketing perspective, names are essentially a brand and Canon has accumulated a great deal of marketing capital in the 7D brand. If you consider that the 7D brand itself embodies the top APS-C body, it does seem likely that it would continue to emphasize that brand, and all that it stands for, and therefore unlikely that it would change sensors.
We can consider this from the standpoint of branding and how Canon intends to fulfill its stated commitment to pro sports/wildlife. Here are some scenario choices, which I would arrange in the following order of likelihood:
1. Canon emphasises the 7D2 "flagship" APS-C status enhancing the 7D brand to include pro wildlife activities as a companion to the 1DX. This of course depends on suitable APS-C sensor technology that can produce convincingly better images, even under low light, than one can obtain by cropping 1DX images to the same FOV.
2. 7D2 doesn't quite make it as (1) above describes, but Canon continues their wildlife niche camera brand with a new APS-H camera body, essentially a successor to the 1D4, that does produce convincingly better photos than the 1DX (or 5D3) cropped to the same FOV. If they cannot produce a "flagship" APS-C body with sufficient IQ to appeal to the the pros, or to compete directly with Nikon, they might still punt with an H body -- as expensive as that would be to continue the manufacturing investment of APS-H for only one body.
2.5: on edit: I guess a less likely (to me) but possible scenario is to put a twist into the 7D brand by making the 7D2 an APS-H body and propelling the 70D to the top prosumer APS-C body. THAT would be a fascinating show to watch, especially on this forum
3. Canon walks away from its its stated commitment to pro sports/wildlife, and produces no worthy crop body companion to the 1DX, and the pros just crop their 1DX images as subject distance requires. BTW, the equivalent APS-C crop is ~6MP.