Some clarification here as it's very much needed going by all the comments:
Him being named to the next Swedish National Team roster doesn't mean he'll play at Worlds.
Sweden will play 7 games spread throughout 3 events, before Worlds. Between each event some players will get cut and some (who weren't available before) added.
Lekkerimäki would be named to the first event, then he'll have to keep earning spots in the future rosters, like Leo Carlsson did last year.
The events:
15-19 April: 2 games against Finland, in Finland.
22-25 April: 2 games against Finland, in Sweden.
30 April - 5 May: Czech Hockey Games (featured Czechia, Finland, Sweden, & Switzerland).
Before the first event there'll also be practices for the players going to it, so his time off would be rather short.