Issue 100-year Treasurys, advocates the Wall Street Journal. It mentions a short note deep on the Treasury website that:
Treasury's Office of Debt Management is conducting broad outreach to refresh its understanding of market appetite for a potential Treasury ultra-long bond (50- or 100-year bonds).
My 2 cents: Why stop at 100? Issue perpetuities!
(I wrote a whole paper on this a while ago, if you want lots of detail and answers to practical questions. Unfortunately the Treasury website does not say how to send in suggestions, and nobody outreached to me, so this