PINE64 promises to manufacture the PinePhone for 5 years, because it wants to be a platform for tinkerers to make mods and to support the A64 in many form factors (phone, tablet, SBC and laptop) so the mods can be used in many types of devices. The communities that make the distros for the PinePhone are unlikely to abandon it as long as there are users still interested in using it.
PINE64 will be supporting three processors (A64, RK3399 and RK3566) in many form factors, which will give people a lot of choice in the future. PINE64 is also planning an SBC based on the RK3588 which will finally give us a competitive chip with Snapdragon, MediaTek, Exynos and A-series, but it looks like it will be a while before we have a FOSS driver for its GPU.