Well, Cameron has basically pushed ALL the onus onto whomever his successor is.
His successor now has to pull the trigger on being in the EU, which could lead to their party loosing the next general election and lead to serious economical issues for the country, and god knows what else (including the huge loss of laws from leaving the EU... most of ours will need updating (if they actually get updated) as the EU laws overrule them).
There is also a chance to stop us leaving the EU via our own parliament (This referendum, after all, isn't binding). We still have to have a vote, in parliament, on the act which took us into the EU in the 70s. This will have to be repealed.
The longer they wait, the less likely it is for us to leave.
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On a semi-related note, I'm honestly disgusted by the jump in racist attacks since the vote.