It will, I suppose, depend entirely on just how successful the Nintendo Switch turns out to be.
The appeal of the Nintendo Switch is in its sheer versatility- here we have a hybrid system that is both, a home console and a portable, and it can be exactly what you want it to be, when you want it to be that. Indeed, one of the biggest things going in the Switch’s favor is the fabled unified Nintendo library- one system to play all Nintendo games on, as all of Nintendo’s efforts, handheld and console, are put on one system.
And yet, according to Nintendo President Tatsumi Kimishima, who was speaking to Kyoto Shinbun (via NeoGAF), a proper Nintendo 3DS successor may yet happen. Kimishima said that Nintendo is open to the possibility, and if there is a market for it, a 3DS successor will come. Whether this is in the form of a smaller Switch that is a dedicated handheld without the modularity, and which runs the same games, or an entirely new system, remains to be seen.
Of course, the statement may still be meaningless, with Nintendo trying to cover its bases in case the Switch should fail- remember the Gameboy successor we were going to get in spite of the Nintendo DS’s release? That never panned out because the DS’s success ensured that there would be no need for it to pan out. If the Switch is sufficiently successful, don’t expect to see any dedicated Nintendo handhelds beyond a Switch SKU designed to be only a portable.