I'm not so sure about Project Fi disappearing.

The fact is, they have a national rollout of Project Fi because they were able to operate in a way that allowed them to resell existing carriers' products as an MVNO. And they were able to offer something unique over existing MVNOs by combining Sprint and T-Mobile's networks, which required a special radio/SIM card combination since the networks are quite different. It had the practical upshot where I live of providing superior service to even the best available networks (which are AT&T and Verizon in my area) and giving me excellent coverage in an area served poorly by each of the networks independently[0].

Ensuring that people have fast, reliable, non-discriminatory access to the internet is within Google's best interest. Assuming the next administration undoes network neutrality, Google could find itself and its products penalized if carriers offer alternatives that don't include surcharges (unlikely, yes, but possible considering many don't have more than one choice for broadband service).

And, speaking personally, working with Project Fi has been wonderful. I've interacted with customer service on three occasions (most recently a month ago due to a software update killing my wife's phone) and they're incredible -- going well over and above what the other carriers have done for me when I've run into trouble. It's particularly nice for me since I have data usage requirements that occasionally balloon in a given month but are often very low -- it's saved me about $80/month as a result[1]. And from what I read, it's a lean business. Since they don't manage the network, all of the phones offered are in-house brands (Nexus and Pixel), there's a lot of overlap everywhere except for customer service[2].

[0] I'm about a year out of date with data since I've had Fi since then, but the thumb area of Michigan had parts that were covered well by T-Mobile, Sprint, Verizon and AT&T, but those places were interspersed with a lot of dead areas. Sprint and T-Mobile appear to almost exist in places where the other isn't so as a result of combining the two, I get 4G through every part of the thumb that I spend a lot of time in the summer.

[1] My data usage is almost always under a gig, but I occasionally run into a situation where I need a lot of data for a few days. As a result, I always kept a data plan that was five times what I required "just in case" because the overage charges were extreme on Verizon when I was a customer and it was "just easier". I probably could have managed to keep a lower plan and only called in when I went over, upgrading temporarily (they used to let you upgrade and backdate that upgrade to the previous month a few times), but I didn't like the risk or the hassle.

[2] When I had this problem with my Nexus phone, I was transferred from Fi support to a much more general hardware support group that sounded like it was specific to the Nexus phones. Despite the transfer, this call was the shortest I've dealt with to get to resolution and I was pleased that the CSRs all had a great command of the English language (the hardware guys had accents but they weren't so thick that I had a difficult time understanding them). Getting a replacement sent over night with Saturday delivery at no charge was really great.