Suddenly we are starting to get a clear(ish) picture, with new rumours and some corrections to previous ones.
Sicily should get one stage, with finish in Taormina. From there they'll immediately transfer to Calabria, where they might have a finish in Crotone. After that, no idea until stage 8 that should finish in Isernia. Stage 9 will be an MTF in Abruzzo, and the new favourite now is the Blockhaus, instead of Prati di Tivo.
Rest day, and then they'll go to Umbria (Terni or Spoleto), then to Emilia where Faenza and Reggio Emilia should be involved. Then a stage in Liguria, finishing in the province of Savona (Beigua MTF still very possible), then Piedmont. It's unclear how many stages here (some say even 3), and if they're also gonna go to Aosta or not. What is sure is that the third week will be on the east, possibly starting in Lombardy, then a stage in Trentino/Südtyrol, then stage 18 with a flat finish in Martellago, stage 19 in Friuli with a passage through Slovenia. This stage should finish in Castelmonte. Stage 20 then will finish in the province of Belluno (Nevegal or Tre Cime or something else). Last stage in Verona.