you have to be kidding me... according to Engadget the RM-877 (aka EOS) just passed through the FCC for AT&T... this means 925 is a just a joke.
I think you are looking at different markets here. T-Mobile is small beans as has US in general been for Lumia range. Lumia 925 is most of all geared for global market and is already out in some European countries.
Lumia 925/catwalk was titled as Lumia 920 replacement since the first details of it leaked, not a successor. Think of it this way, as EOS comes out to stores likely somewhere in Q3 you will have 599 euros EOS and
much more compact aluminium build Lumia 925 globally that price will likely be in the ~450 range by then. By the end of this year we will have quad core, 1080p phablet made possible by the WP8 GDR3 update, Nokia EOS with its 41MP camera and Lumia 925.
At this moment its hard to compete against your own phones when you are selling at tops 2 million of flagship phones every quarter. That wont be a problem. Nokia is simply squeezing everything out of WP8 GDR2 it can before GDR3 lands later this year.
From what I've read the EOS will have basically the same specs as the 920/928/925 except it will have the bigger camera.
Yes, that will most likely be the case. With GDR3 in Q4 we will see similar line of flagships as with Lumia 920, ATIV S and HTC 8X.