This family of theories has been around for a while, 1491 by Charles Mann discusses them extensively, and that book is from 2005. Reliable evidence is sparse though, so this could be a major contribution.
It's actually been longer than that. The site at Monte Verde [1] in Chile seems to have been widely accepted as a pre-Clovis site nearly 20 years ago (1997 according to Wikipedia [2]). Awareness of the site, at least among the archaeological community predates that (1989 [3]). The first radiocarbon dates indicating a pre-Clovis origin for the site go back to 1982[4].
The idea that Clovis was not the earliest culture in the Americas, and the commensurate theory that the earliest colonists must have been traveling by boat [5] goes back decades. I know I've been reading about it (in the popular press no less) since the 1990s. It seems like every article I read about it makes it seem like some new and revolutionary idea. The only conclusion I can draw is that archaeological science operates on time scales only slightly shorter than those the archaeologists study.
[1] https://en.wikipedia.org/wiki/Monte_Verde
[2] https://en.wikipedia.org/wiki/Monte_Verde#Acceptance
[3] https://en.wikipedia.org/wiki/Monte_Verde#Diffusion
[4] https://en.wikipedia.org/wiki/Monte_Verde#Discovery (third paragraph)
[5] I'd like to give you a citation for this, but this theory, as far as I can tell has no official name.
[Just quoting myself from https://news.ycombinator.com/item?id=12603556]
"The coastal migration hypothesis" - https://en.wikipedia.org/wiki/Coastal_migration_(Americas), which should not be confused with "the Southern Dispersal scenario (also the coastal migration hypothesis)" at https://en.wikipedia.org/wiki/Southern_Dispersal.