Hmm.
Depends on who's doing the obstructing. For example, the SNP MPs are likely to vote to block Brexit, but are hardly going to be punished for upholding the will of Scottish voters in the referendum, so that's not going to help the government. Plaid Cymru might vote against but they have basically no MPs anyway so who cares? That leaves Labour and the Lib Dems -- for Lib Dems, they are pitching themselves as the party of the 48%, and on that basis I would expect to see their support go up in 2020, rather than down.
Only Labour and the Tories can be hurt by blocking of Article 50, therefore. I think it would backfire on the Tories more, because they hold the majority in Parliament that should be enough to force through the legislation -- ergo, it would be entirely fair to say that Brexit, if it was blocked in Parliament after all, was blocked by disgruntled Tories rather than by Labour.
There's a lot that can happen in 2020, anyway. Heck, a Tory landslide is possible too. What I would say is that trying to rule out a Labour (Corbyn) victory is premature. Labour wouldn't have needed Scotland in 1997, for example, to hold a majority.