As someone who owns a small dual sport (WR250R) and S10, but who also lusts for a T7 just to fill narrow band between, here's my nickel's worth.
Take a look at what you want to do with motorbikes. The T7 is great between offroad and highway, but I don't think it can do knarly offroad AND be a tourer. Why? Tires and general setup. It does depend on the nature of the offroad you want to do, and the T7 can do each. But for knarly offroad, compromising on the tires plus the added weight of the T7 make it less interesting to me for knarly offroad. And long road trips make the T7 less desirable (comfort, cruise control).
I bet your CRF300 is pretty capable. My wife has a CRF250L. We've loaded our 250s with camping gear, put on some dirt-oriented 50/50 tires and been able to manage multi-day trips on sand and gravel (minimally maintained forest roads), plus pavement (not doing knarly offroad that loaded). While we aren't going to hit interstate speeds, we've had no issues on other highways. I'll add that I had my rear shock spring updated and shock tuned, and my wife has a Racetech suspension setup, but otherwise no magic.
Do I want a T7? Yes. It would be like having ice cream after a meal - fills all the nooks and crannies. For a lot of offroad and getting to the offroad, I think it's a fantastic beast. I wouldn't dissuade you from a T7, but if you are willing to have two bikes (n+1 syndrome), I'd probably get the S10 and first and then really test how you want to ride, pushing the 300's capabilities for what you want offroad.
Now, you may already have a good sense of what and how you plan to ride. The T7 may be a better choice than the 300. I sort of see that possibility on my horizon. But I bet that 300 can do more than you think, other than top-end speed.
Eville Rich
2016 S10