Binding Blade was most likely that cancelled 3DS remake since it was a kinda short handheld game.The Fire Emblem bit is a little bewildering.
Fire Emblem Echoes: Shadows of Valentia came out in 2017, very late in the 3DS's life. It was a stopgap project for the team after Fates finished but before Three Houses could go into full development. They were already looking toward the Switch for future projects.
Obviously we now know that Three Houses was made mostly by KT, rather than IS, so it's been an open question what the rest of the IS FE team has been working on, but... another 3DS game? I suppose it makes some sense given their limited scope of technical experience compared to KT, but it's still baffling that they wouldn't have moved on to Switch.
In fact, look at this developer quote from an Echoes interview:
Hopefully the upcoming Switch one includes Blazing Blade to make it an actual complete story.