Sony said last year that it's not going to focus on the US market for a while, but it seems they have plans to return to the US market soon, and also has big plans for 2015 to sell up to 80 million smartphones, as it "puts more resources into the U.S. and Chinese markets." Sony will reportedly put "money and people" into the US and Chinese market to achieve that goal.
Sony has been making a lot of improvements to their phone line-up lately, they've been getting more attention from the media, so it's a matter of time before they make a deal with US carriers, too, if they see there's pent-up demand for Sony's phones in US. That's historically been Sony's main problem in US.
Their most recent deal with a US carrier is for the Xperia Play, that phone that came with an integrated controller, but because at the time Sony used to be so bad at making phones compared to the competition, the phone was launched with obsolete specs that nobody wanted anymore. It's one thing to have older specs for a normal phone, but it's a lot worse if it's for a so-called "gaming phone".
Since then Sony has tried to sell its phones off-contract and through some retailer deals, but I don't think that has made much of a dent, which is why they said last year that they want to take a complete break from US for some time. But now it seems they have an attack plan, they've made some money, so they have some to invest in promoting the phones in US.
I believe it would be tremendously helpful for Sony to make the next Nexus phone, with the same great design we're seeing in their latest models (but smaller bezels!), and a really good camera, which combined with the improvements to Android camera software that Google is working on, it should be quite good, even if it won't be the most expensive mobile camera out there (given the $350 price target).
The free publicity Sony would get for making the next Nexus phone would be invaluable to Sony, and invaluable for a really big launch of its other products in US in 2015, even if they won't make a lot of money from the sales themselves. But they'll get something much better - great branding in US for being a company that makes quality products and a lot of momentum.
The Nexus could be their lift-off platform that could help them take even on Samsung, so I hope they aren't downplaying this opportunity, if they can indeed take it, and Google isn't think about some other company (although we're running out of good choices for the Nexus, and Sony has never been picked anyway).