"It's time for everyone to..." Those always seem to me fairly incantatory grounds for making a major decision. I think there's every reason for the Opposition to bide their time and use their control of the general election agenda.

Corbyn may believe he knows how to campaign on other (vital) issues than Brexit, but the Brexit and anti-Parliamentary noise Johnson and Demonic Cummings can drum up at the moment will, I fear, drown his voice. No election should be held yet, that Johnson can come out of with a comfortable majority (and an agreement with the Brexit Party would be perfectly on the cards in order to ensure that). What we are not thinking much about is how he would use it over five years. Legislation to hobble Parliament (rather than reform it) and increase the power of the executive with plebiscitary backing would imo be the minimum.

So yes, a caretaker government is to be wished for, but the potential parties to it cannot or will not agree. Until they do, leaving the organisation and framing of an eventual referendum in Johnson & Demonic's hands would be utter folly, the result would be a greater manipulation even than 2016.

Things are going to slide, slide in all directions
Won't be nothing, nothing you can measure anymore
L. Cohen