9th Jan to 18th Mar: I concur, that is the inherent BTC increase rate.
Your blue line is correct IMO.
If the USD doesn't crash one BTC will have a value of ca 1000 USD in a couple/few years. The blue line will even give the predicted month. Spike(s) could see an ATH over 1000 USD months in advance of the BTC value actually being so.
Fine graph.
I agree that the blue line is the "real" one, but the question is should you be willing to pay a premium now for BTC, to be able to ride the blue line in the future?
I mean, consider a scenario (I know odd, but it, or a variation, is possible) in which BTC went above the "real" blue line, then went flat until the blue line "caught up." People that bought at the top plateau would still be in pretty good shape.