Samsung announced the Galaxy J4 and Galaxy J6 back in May. The latter got renamed as Galaxy On6 for online sales in India, and according to xda-developers, the phone might have a Plus-sized version very soon.
A developer found firmware files of a Samsung phone, codenamed j6plte, or J6 Plus LTE. The rebranding of the J-series to On-series is not new, so it might also appear on Flipkart or Amazon as the Galaxy On6 Plus.
The firmware files for j6plte correspond to a model named Samsung J6-Plus LTE CIS SER, where the last two letter combinations reveal the device might be headed to the Commonwealth of Independent States (mostly former Soviet republics) and Serbia. It could have a Snapdragon 450 chipset, opposed to the Galaxy J6 that runs on the Exynos 7870 Octa.
There is also the possibility the phone was scrapped and such device to be canceled, but as we see so far, Samsung is really into making bigger variants of its more affordable phones, given the Galaxy A6+, Galaxy A8+ and the Galaxy S9+.