According to rumors from Gillig at the 2017 APTA, plan is they are going to show a prototype articulated model at the 2020 APTA.
Some reason they waited is apparently there used to be too much competition and Gillig was going thru their move to the new Livermore facility.
I see why they are going for this now, not only are larger systems moving to Gillig buses, but those larger systems also usually operate artics and have to get either New Flyer or Nova which of course reduces fleet commonality. This would be major for Gillig too because they would be the only bus manufacturer to offer all 30, 35, 40, and 60 foot models.