The teaser trailer went about it all wrong. Starting with 1991 and having the dates tick by, showing screens of Sonic 1, 2, 3, & Knuckles, and 4 Episode 1, and Episode 2 implies that this is the successor to the originals, which it is not. It also lumps Sonic 4 in with the classics, which given Sonic 4's reception, is a bad decision on the trailer makers part. Instead of thinking about Sonic Runners, all I'm thinking about is SEGA's mismanagement of Sonic 4, and how weird it is to see them actually grouping it with the classics. Especially when Sonic Generations really was much more connected to the classics given it was a fully produced Sonic Team game, and played much more like the originals.
And then there are the handheld games, which given Runners being mobile, doesn't runners have more in common with the likes of those? But after reading the Iizuka interview, Runners is sounding more like Jump and Dash, which isn't a bad thing because Jump especially is an enjoyable mobile game, but tying Runners in with the classics is just plain stupid.
Having said all that, I do think the game could be enjoyable, I just think the setup for the teaser was all wrong. As mentioned, Rayman Jungle Run is a really fun title, and from the sound of it this is not an endless runner, nor are stages randomly generated. It sounds like we'll have pre-made stages with 50 in total, which should appeal to speedrunners who are constantly moving forward anyway.
tl;dr the teaser goofed in linking it with the classics, Runners could be good, but making that connection has backfired in the past (see Project Needlemouse)