The meme is a parody take on Democrats knowing their chances of winning the election is low. It's not to be taken literally as an either or fallacy. Why not both? They can do both, but the likelihood of either succeeding is low. Even if Trump is impeached - he will certainly be exonerated in the Republican controlled senate.
In regards to static support for months. The polling data prior to the 2016 election showed Hilary winning with certainty. I don't put a whole lot of weight into polls - especially when they're being conducted by organizations with clear political bias.
Yes, we'll see, but I suspect it will go exactly how I've just described it. Trump will be impeached in the house, exonerated in the senate, and the American public will see the impeachment hearings for the partisan clown show that they are and reelect president Trump by an even wider margin than the first time.