Do bear in mind that the Oppo Neo 5 (2015) is different from the aged Neo 5 (relatively speaking, of course) which rolled out last year, which would fit in nicely with the naming convention in terms of the designated year. It does carry a spot of the Oppo R1x style, and while the hardware on both handsets are more or less similar, the differentiating factor would be the chipset within.
The Neo 5 (2015) will sport an MT6582 SoC within, where it will run on a quad-core 1.3GHz Cortex-A7 processor alongside a dual-core Mali-400MP2 GPU. As for the “s” suffix in the Neo 5s, that would most probably stand for Snapdragon, since this particular model will carry the S410 with a 1.2GHz quad-core Cortex-A53 processor and Adreno 306 GPU. LTE support would be the main difference between the two, which is missing from the Neo 5 (2015), although do take note that the Neo 5s will be regionally dependent where supported LTE bands are concerned.