I am for 0w20 but I am playing devils advocate a bit here.
You'd think if you wanted to make a statement about superior fuel economy and protection, the very works printed in the TSB over the 30wt oils, you would have it readily available, and it be competitively priced. I think there would be very few owners that own 2006-2008 toyotas listed ready for the 0w20 on that TSB that have been told about it from the dealership, or approached at oil change time from the dealership that hello, this is the new direction we are going with oils.
I highly doubt that the fuel savings alone for 0w20 at $8-10L would make up the difference over 0w30 at $4-5/L for 0w30 over an interval. The same goes for the conventional 5w20 vs 5w30, and people in general are having a hard time with it.
If toyota wanted to really make it mainstream and catch on, they would offer it at a very close price point difference and have the proof to back it up and let all the owners covered by that TSB know about it. After all they are trying to change the mindset of owners that have up until this point used 30wt oils, had they cars go for a gazillion miles and it worked just fine, why pay more for what they are unsure about and don't know.