A local article today claims the Friulian stages (Zoncolan and Gorizia) are happening in this order on May 22 - 23, which makes them stages 14 and 15. The same article says the next day they will start from Pordenone and head into the Dolomites (hinting at the Tre Cime). I doubt they won't have a rest day after stage 15, but regardless, this fixes a bit of the route. The route will be coming from the Veneto region, and I'm going out on a limb and guess stage 13 will be an ITT in or near Verona, possibly from Desenzano del Garda, which was rumoured a while ago and now it would make sense. Only the third week is uncharted territory. Stuff has to be happening in Trentino and Valtellina, but we don't have enough rumours there to get a good idea.
(EDIT: Forgot to mention, Zoncolan from Sutrio, like in 2003)
This is a new (hopefully good) sketch:
1 Torino ITT
2 Santena - Verbania
3 Arona - Alessandria??
4 Piacenza?? - Ravenna
5 Rimini?? - Perugia??
6 Foligno?? - Monte Compatri
7 ??? - somewhere towards Foggia
8 Foggia - Castel di Sangro?
9 L'Aquila - Campo Felice
RIPOSO
10 ??? - Montalcino
11 Siena - Florence area?
12 ??? - Mantova
13 Desenzano - Verona ITT
14 Treviso?? - Zoncolan
15 Grado - Gorizia
RIPOSO (here or after stage 16)
16 Pordenone - Cortina or Tre Cime di Lavaredo
17 -- 20 ??? (Montespluga??? Montecampione??? Stelvio??? Who knows)
21 Milano ITT