Walcott faces six months out and will miss the World Cup after suffering anterior cruciate ligament damage in Arsenal's FA Cup third-round victory over north London rivals Tottenham earlier this month.
Wenger revealed the 24-year-old is progressing well since having surgery on his knee last Saturday, insisting he was optimistic that Walcott would be back at his best for club and country next season.
"The damage was real in the knee so he will have to take the needed time, so let's not be hopeful that he will go to the World Cup - that is not possible, but overall his long-term future is very positive," Wenger told Arsenal Player.
"It is about being fit for next season now."
Wenger has a number of injury concerns ahead of Saturday's visit of Premier League strugglers Fulham.
Nacho Monreal is a doubt after twisting a ligament in his foot during Monday night's win against Aston Villa, while Thomas Rosicky's participation is questionable after breaking his nose during the game.
Striker Nicklas Bendtner is still nursing an ankle injury and Thomas Vermaelen remains sidelined, along with midfield duo Mikel Arteta and Aaron Ramsey.
But the Arsenal manager has been boosted by the return to fitness of Alex Oxlade-Chamberlain, Kieran Gibbs and Lukas Podolski.
He believes he has sufficient depth in his squad - particularly in midfield - to continue the form that has seen them stay top of the Premier League past the halfway stage of the season.
"In midfield we have plenty of quality players who you can rotate easily without really feeling, 'today we are weaker'," Wenger said.
"We have fantastic players in midfield and it always allows us to keep what we call the 'engine' of the team fresh.
"It is a real team effort. Maybe because every player in his position has a strong personality as well - you have that feeling.
"I would say purely on the football front it's true that we only have excellent players in every position and that allows you to have different types of teams that can really be efficient."