There's been a gradual trail of breadcrumbs leading to this idea, but as of this moment, there is still nothing confirmed. That said, this is still very much a rumor, albeit one that is beginning to make more and more sense, so still take it with a grain of salt. The Shenmue rumor mill is once again beginning to turn as word has spread from Rice Digital via a "source close to Atlus USA" who has revealed that both Shenmue 1 and 2 will be getting HD Remasters that will release sometime this year. It is backed up by the claim that Shenmue 3 may be slipping into 2018 as it is currently scheduled for the always-flexible December release window later this year.
This is not the first time we've heard of an HD Remaster release for Shenmue 1 and 2 either as SEGA themselves revealed back in May of 2016 that it was a project that they wanted to pursue but noted that it was "not as simple as porting the games to current platforms." They referenced a desire for quality and "complications from licensed products that were included in the original games" as major hurdles but that they were "currently investigating how to make it a reality."
That was almost ten months ago, so there has certainly been a decent amount of time in between then and now. This is also not to mention that "Shenmue HD" and "Shenmue Remaster" were registered as official domains by SEGA, but it could also be just a placeholder.
Given the prolonged silence surrounding Shenmue 3's development, it wouldn't be surprising at all to see the game pushed back into next year. Also, it's been almost two years since the game was revealed at E3 2015, so SEGA may also be feeling the need to re-energize the brand on a larger scale amidst the silence, and HD Remasters would fit that bill as well.
Regardless, we will just have to see what happens.
Source: [Rice Digital]