Hellishly expensive lens if you want it to reach 560mm.
This lens plus TC plus 7D II will set you back close to £4000.
Now a Tamron 150-600 (or the equivalent new Sigma C - due March) plus the new hi-res 760D (coming soon) will give you much much bigger images to work with......for only about £1700!
Before you buy either 150-600 make test that it works well on your crop. The Tamron is great on FF but it is not as good on crop. The 100-400mm II does give good images on the 7DII.
I've seen this mentioned several times but can't find a good reference that quantifies this. TDP only has the Tamron on FF. It would be interesting to see it on a 7DII. Did I miss a post somewhere?
I seem to get pretty good results with the Tamron on both my M and T2i, ranging from nearby targets to moon shots. On the 6D it required AFMA +8, but the 550D AF (no AFMA) seems to handle it fine. The differences I've noticed so far are the same as any other FF/crop comparison I've done. Since the Tamron doesn't take my Canon extenders the extra reach on my crops is sometimes beneficial, such as shooting the moon.
I am considering the 100-400mm II for a smaller/lighter solution since I already have both extenders. Even with AFMA my copy of the Tamron is really only sharp up to 400mm (consistent with TDP). In many situations I'll take a shot at both 600mm and 400mm so I have a choice in post.