Since season 26-27 both visited South America, & 25-27 visited Africa, this season will most likely visit 3 continents, MAYBE 4 if the budget allows for Australia. However, I believe they could consolidate this for having additional legs in North America. Canada & Mexico seem most obvious, but some jungle legs in Costa Rica or a visit to Tikal in Guatemala would be so fantastic!
I assumed for this season will still likely to visit 5 continents, the third season in a row after seasons 26 and 27. The race will use a plenty of budget that allow to start the westward route from North America, down south to Oceania (Australia), then up to Asia, and down south again to Africa and head up North to Europe again. For this season, Africa will finally beat its streak of three straight season visits (seasons 1-3, 5-7 and 10-12). Europe will have four different countries in each leg. Slovenia would be nice and has a scenic landscape. The urban legs in Spain (Madrid) and Ireland (Dublin) would be thrilled and have beautiful places. I believe the penultimate leg in Ireland would be awesome. Madrid has neither visited nor have a full leg in American TAR, and Dublin as well.
6 continents: TAR5, TAR11 (2)
5 continents: TAR2, TAR7, TAR9, TAR13, TAR16, TAR18, TAR20, TAR22, TAR26, TAR27 (10)
4 continents: TAR1, TAR3, TAR4, TAR6, TAR10, TAR12, TAR17, TAR19, TAR23, TAR25 (10)
3 continents: TAR14, TAR15, TAR21, TAR24 (4)