Images of this alleged OnePlus 7T Pro were posted to the Chinese social media website Weibo, and don't really give much away in terms of appearances. From what we can tell, not much (if anything) has been changed with regards to its display or the pop-up selfie camera mechanism (which is wicked cool to see in operation). Most of the design details surrounding the phone are unfortunately obscured because it is enclosed in a rather ugly and beefy case.
Inside, however, we might have a clearer picture of what OnePlus has in mind for upgrades on the OnePlus 7T Pro. When the OnePlus 7 Pro launched earlier this year, it was powered by the [at the time] flagship Qualcomm Snapdragon 855 SoC. Since that time, Qualcomm launched the Snapdragon 855 Plus that features a higher clocked "prime" core and a faster GPU, which raises performance across the board. If external changes are going to be minimal, it would make sense for OnePlus to play up the performance angle.
We should also expect some increases to internal storage capacity as well. With NAND prices crashing (as Samsung has seen first-hand), it wouldn't be out of the realm of possibility to see maximum storage doubled to 512GB UFS 3.0 NAND. We don't see any reason why OnePlus would go any larger than the already bonkers 12GB LPDDR4X memory, but we could possibly see a slight increase in battery capacity to satisfy the brawnier SoC.
Of course, this is all speculation at this point, but all signs point to a OnePlus 7T Pro launching in 2019. After all, we have last year's OnePlus 6T as a frame of reference. You can read the Hot Hardware review of the current OnePlus 7 Pro right here.