I may consider OnePlus 6 if it has better camera than pixel 2 but I doubt it.
It won't... Imaging requires vast R&D resources as software has far surpassed hardware as the driver of quality. The best cameras on the market are in phones from Google, Samsung, Huawei and Apple... Four companies with massive resources brought to bear on camera performance. Not to mention the pull to have hardware vendors provide bespoked components to match their needs. OnePlus is simply grabbing good sensors and adds a few tweaks to the default ISP that Qualcomm provides in the SoC. That only gets you so far.
Back to the OP... Nope. The 6 will be a good phone, at good price, and it'll do pretty much everything quite well without really standing out in any particular area. It is, by all accounts, what you would get if you cobbled together a bunch of excellent off-the-shelf components.
I don't see anything that would have me say 'Oh, I NEED that!'