The 22-year-old could feature from the start against the hosts, Italy and Samoa after impressing for his club this season in his 16 league appearances.
"Grant Gilchrist is a special player," Johnson told the Scotsman. "People forget his run up to the French game was absolutely terrible because of missing three or four games with injury. His first real run out was against the French - for a 22-year-old boy that was a big ask.
"There is something good about Gilcho. He is big and abrasive. The (rugby) world watch out - if we get him the way we want he will be a special player. This is part of his learning. We are not going to kill him (but) it is a good development.
"We are up against pretty formidable sides but in three or four years' time, if we get Gilcho right, and this tour is part of it, the world will know who he is."
Gilchrist is one of eight Edinburgh players selected in the Scotland squad for the tournament in June. That includes the Dutch-born Tim Visser, with Johnson expecting the experienced winger to take on more responsibility having found his feet on the international stage.
"Tim understands he is not the new kid on the block," added Johnson. "There will be people around him who are going through what he went through a year ago. Hopefully he will accept that responsibility."