The Netherlands is likely to be strike-free in public transport this summer. NS was first with strikes, but has a new collective labor agreement since early this year.
What followed were strikes for the CAO OV (the collective agreement for regional bus transport), where the unions have reached a definitive agreement with the employers earlier this month.
Less sure is the situation with the CAO Multimodaal (collective agreement for the regional rail operators, partially also involving bus franchises) where negotiations have been finished but the voting for union members is still ongoing, so not yet sure they'll accept the result of the negotiations.
GVB Amsterdam, HTM The Hague and RET Rotterdam have seperate collective labor agreements, but I'm not aware of ongoing negotiations there. So risk for strike is relatively low.
The most significant threat to visitors is most likely the summer holiday itself: staff shortages are still very much a thing in public transport. It differs a lot from region to region: some have come from much worse situations and are on the way up again in service reliability, but other regions still have significant cancellations. Practically nowhere the full timetable is in operation at the moment.
For bus drivers, the labor market is just extremely tight. I've even seen reports that operators loose staff which elected to apply at another operator in a nearby region. And as the age is high, lots of staff retires as well.
My regional bus operator for example has already decided to run less-used routes using small neighboorhoud buses for maximum 8 passengers this summer. Those vehicles just require the same driving licence you'd need for a car, thus freeing up drivers holding a bus licence for the services needing a large bus.
