It is a marketing buzz for sure. And potentially a strategic misstep.

It is not clear at all what will the cryptocurrency do, and why do they need it: "PeiCoin's blockchain platform is woven seamlessly into the architecture of the OnePlus forums".

First of all, OnePlus is a Chinese company. Up to date, China has been very clear on cryptocurrencies. They have banned all of them. So OnePlus will be integrating some 3rd party crypto. It raises legal issues in my opinion.

What OnePlus should have done, is create a blockchain smartphone. Market it as a secure and convenient way to use your phone. Then run an ICO, which soon should be possible (there have been news from China recently that they may allow ICOs). Collect funds to build a better smartphone. Those people that have their tokens will be able to buy them with tokens and get smartphones earlier with special design or some other perks. When people bought smartphones OnePlus can issue/redirect tokens once more, to build another smartphone.

The biggest benefit they'll get, is that they will be able to build a first blockchain appstore (competitor to apple and google). That could be the biggest advantage of going blockchain for OnePlus. Cryptocurrency is questionable.