I hesitate to call myself a Marxist, in part because the label encompasses so many different schools of thought, though I probably could since I find his ideas useful. I will make one quibble with your take: so far as I know, he expected socialism to follow different paths in different countries. The closest to a prediction I remember is this:

“there are countries — such as America, England, and if I were more familiar with your institutions, I would perhaps also add Holland — where the workers can attain their goal by peaceful means.” — Karl Marx, 1872 speech in Amsterdam