It would have to be very serious for the government to implement a strict curfew again. There is not much appetite for another heavy lock down. I think we'll see smaller gatherings and more enhancement first. Even if they are forced to lock down, it will only be long enough to contain an outbreak (3ish weeks) so June will be safe.

Airfares are mostly changeable these days so I'd book the tickets and continue as planned until something really happens. I expect mid-June to be just like now. It's possible there will be some relaxing of protocols by then but I'm not overly hopeful. The government will have to change their position on 70% vaccination for protocols to change by then. I was somewhere in the 6000-7000 people vaccinated group and my next shot isn't until 28 May so I won't be "fully vaccinated" until 11 June.