That's the thing...upgrade. Upgrade to what? I mean, 1080p is 1080p regardless of whether or not its IP or Coax. At one time, I'm pretty certain everybody though coax would never support High Definition cameras. But they do. Who's to say that coax one day couldn't support 4k?
You are missing the true benefit of ip cameras. Let me list a few.
1) You dont need to homerun each camera to the NVR. This allows you to easily hide the NVR and can save LOTS of labor time and cost.
2) You can use a second NVR hidden somewhere on the network.
3) IP cameras can be had with SD card slots as additional backup.
4) Lots more camera options
5) use of advanced motion detection like line crossing to avoid false alerts. I believe line crossing is only supported on 1-2 analog cameras on most of hikvisions TVI systems.
Most importantly if you dont like the NVR for whatever reason (lack of features for example) you can easily move over to a pc based vms..with TVI cameras you are stuck with basically the same NVRs.
Finally, there is NO benefit to TVI, except for price, but your budget allows for a full ip system, so why not.