IDK how they are going to have specs that compete with Xbox and Playstation and make it portable with decent battery life.
Simple: Specs won't compete with Xbox or PlayStation. I think it will have the 8GB of RAM that Xbox and PlayStation do because it's cheap and makes your system easy to develop for.
I'm not even sure processing and graphics between mobile and desktop systems can be compared. If you were to compare them, it doesn't look very good...
Check here the SunSpider benchmark (tests CPU, graphics, and software, so not great, but...):
http://www.macworld.com/article/3008554/ipad/benchmarks-the-ipad-pro-is-the-fastest-ipad-ever.html
iPad Air 2 - this is similar to NX performance
And then Surface 4 Pro, which is not even a real computer, beats it by 50%.
And battery life will be the opposite of what you're thinking: About 10 hours. That's how long good full-size tablets (>= 8 inch diagonal) batteries tend to last.
Nintendo says the Wii U tablet battery lasts 8 hours. Whoops, that's the high capacity one. The standard one lasts 4 hours. No worries though, I think.