10 year versus nominal GDP:
Econompic has a great series relating nominal GDP growth versus the 10 year and the long term patterns are impressive.
Note how during the rise in nominal gdp growth rates from the 60's to the 80's interest rates were below nominal gdp and this pattern flipped as nominal gdp growth rates declined.
90 day tbill rates versus 10 year:
Rarely does the spread between the 90 day tbill and 10 year rates go beyond 4% and with short rates at zero this puts a cap on interest rates further out the curve. With 10 year rates at 2.22 this does provide some upside to the range of interest rates, but those recently calling for 10 year rates higher than 4% were calling for something truly exceptional.
Until we see nominal GDP growth really perk up and/or the Fed start raising interest rates I find the possibility of the 10 year going above 4% unlikely.
Disclosure: I own long term treasuries in personal and client accounts.