The term "Medicaidization" dates back to at least 1990 (here in JAMA) but is still used pretty infrequently. See a 2012 article about Medicaidization of social services (here) and an article on "Medicaid for All" at Frenkel Benefits, here. I think the term is a useful concept - narrow networks, lots of downward pressure on pricing - and have used it in this blog a few times (here).
In May 2017 at Health Affairs, Margaret Murray and Mike Adelberg produce a well crafted and insightful article on Medicaidization - find it here. They note, for example, that Exchange marketplace plans may likely also provide Medicaid managed care plans, suggesting shared expertise.
As of today, the term only has 2 hits on Pubmed - from 1990 and 1991 - but I think its use will pick up.