It's a simple math problem. What is the total amount of money you've invested creating per year as ROI?
Let's say you put 20 percent down, plus 100k in furniture, repairs, rehab, setup costs (months of mortgage during setting up etc) that's 300k invested. You're making 120k profit a year (plus some equity appreciation of course)
120/300 = 40% ROI. You will be very, very hard pressed to find a better property return than that. However! You said it could sell for 1.9 million. So if you sell, you're getting back 200k + 900k (value increase) roughly, so 1.1 million.
Now the math asks - could you invest that 1.1 million and produce more than the 120k profit a year you're getting now. In stocks? Probably not. In other STRs? Yes, but you'd also be looking at months, if not years to find enough properties to get that back (also consider you'd have to change markets, otherwise you're just exchanging one house for another, and you reap no significant benefits). Also consider if your income can support a mortgage for 1.9 million. Especially once you sell your cash producing property.
Overall I'd argue keep your 40 percent ROI property. Use the profits to buy more in a year or two. But that's my personal preference of buy and hold, instead of flip. You have to ask yourself which type of business do you prefer?