As many have said, it entirely depends upon what you want and need to do with a portable computing platform.
I use my 2014 MacBook Pro and my iPad Air 2 mostly for personal stuff. I also have a 2010 27” iMac. Work is mostly on a Windows 10 laptop with a docking station and dual monitors, provided by my employer.
I say mostly because occasionally on a lengthy project I’d rather work in Excel in MacOS. Likewise with Word.
But lately I’ve come to the realization that I rarely use my MBP, at least for the past year, but use my iPad daily. My iMac takes care of the rest.
So in the interest of simplifying, yesterday I sent my MBP off to a company that purchases used Apple stuff. I could probably get a few bucks more by selling it myself, but the transaction costs (mostly the time and effort) given where I live would likely eat up those few bucks.
My intent is to see what new IPP models are announced at WWDC, or whenever Apple gets around to announcing them, then decide what to buy. My iPad Air 2 works just fine, but the IPP is appealing to me for a couple of reasons. The anticipated payment for my MBP will cover nearly all of the 10.5” IPP, including Smart Keyboard, case, pencil, and AppleCare. Then again, I’ll spend some time trying out the larger IPP before deciding.
The heavy lifting for my needs will be performed by my iMac, at home. But it’s a desktop, and your question was about being a laptop replacement.
Clearly, my expectation is that the IPP will replace the MBP for my purposes. My current IPA2 is, in my opinion, a stellar device for what I use it for. Buying an IPP may be strictly unnecessary, but as much as I use that platform, I believe it will be worth it.
Forgot to respond to the question of mouse support and file management. I don’t recall ever wishing my IP had a mouse. Files go to Dropbox.
Again, as for you or anyone else, it entirely depends on what you want and need to do with a portable computing platform.