This particular patent says 240mm lens length (right?) so that puts it a tad shorter than the 400mm/5.6.
And way longer than the nice 70-200 collapsed size if that's the case.
The 70-200L is 200mm (internal zoom), and this is on the very edge of portable ... the 70-300L is only 143mm collapsed.
This puts this new patent in another class entirely, and thus the zoom range is a bit bit strange - who would want to use this @70mm except for dedicated usage cases when very high flexibility is required? The difference between ~300 and 390 isn't that large w/o tc, so if I were to use this instead of the 70-300L the new lens would have to have terrific iq ... which also means very high weight & price.
I can see many applications, especially in sports and action. I shot a lot with the 300 F/2.8 IS II last year, and definitely was aching for some extra reach.
The 70 - 300 has been tempting, but my 70-200 F/2.8 IS II I think has slightly better IQ, not to mention a lot faster, so have a hard time justifying dropping $1500 for just having 100 extra MM
Now the 200-400... Car or lens... Car or Lens...
So for the 70-400 with the same aperture range as the old 100-400? I only stayed away from the 100-400 because I heard it was a dust sucker, have used it/rented it twice and it was decent, but the 300-400 range can be very convenient, especially when you don't have to swing / switch bodies as object gets closer.
If the 70-400 has the slightly better IQ and better sealing, and no more push/pull I think it is a decent upgrade.
I still will likely pull the trigger on the Tamron because of price, and for what I have seen the IQ is decent. Even if the 600 really needs F/8 or F/11, I figure getting upwards of 500mm for that price still is a bargain, and makes a nice compliment of 70-200 on one body and 150-600 on a second.