OnePlus has been on a bit of a roll since... well, its inception. All of its flagship devices have been well-received and have sold well, leading us to believe that its next major launch could continue the tradition. Even though the phone hasn't been officially announced yet, we know that it's going to be called OnePlus 5, skipping over "OnePlus 4" entirely.
Last fall, OnePlus released its OnePlus 3T, an upgraded OnePlus 3. That in effect should have been called OP4, simply because it's the phone to preface the OP5T. But, it's just a matter of semantics, we suppose. According to The Verge, which was given exclusive information by OnePlus, the company's next flagship is going to arrive this summer, and will bear the OnePlus 5 name.
OnePlus' 3T, soon to be replaced with the OnePlus 5
Why the number 5? The Verge explains the odd reasoning: "One thing that OnePlus says did come into play was the number five jersey of former NBA player Robert Horry, who a number of OnePlus employees consider themselves fans of." If that sounds a bit too "out there", consider the fact that there are two Horry paintings gracing the halls of OnePlus' HQ in Shenzhen.
At this point, OnePlus itself isn't admitting to more than the name and tentative release date, but some leaks have given us a glimpse into the future. In some cases, 6GB of memory (just like the OP3 and OP3T) looks to be bundled, but other rumors put the tally at 8GB. That seems a bit extreme for a smartphone (not that 6GB isn't), so if there is in fact an increase, we can hope that OnePlus has a good reason for it. Maybe the smartphone could plug into a monitor and double as a PC, a la the ill-fated Lumia 950 XL from Microsoft.
It's also rumored that the OP5 will sport 128GB of storage, though it's not clear (of course) whether that's the default size, or simply an option. 128GB does seem a bit grand by default, but 64GB would make a lot more sense. Also likely to be included with the OP5 is Qualcomm's high-end Snapdragon 835, which compared to the OP3/OP3T's 820/821 (respectively), doubles the number of cores, upgrades the GPU, and will have improved cellular capabilities. It's also built on a 10nm process, versus last gen's 14nm.
There's no telling at this point what OnePlus will charge for its upcoming flagship, but we can hope it will keep in line with the previous models, since its middle-of-the-road pricing is undoubtedly one aspect that has helped the smartphones sell so well.