Taylor Swift and Travis Kelce have yet to send out save the dates for their wedding ... either that, or we got some bad news for Taylor Lewan -- 'cause he tells TMZ Sports he's "fully expecting" an invite in the mail!!

We caught up with the ex-NFL star and current "Bussin' With the Boys" podcast host this week ... and considering he's been buddies with the Chiefs superstar for years, we had to ask if he's gotten word on when the engaged couple will meet at the altar. Getty

"I do not know when they're getting married," the former Titans lineman claimed. "I do know that I fully expect a wedding invitation from Travis. He's been on the show multiple times."

Lewan went on to praise Kelce ... saying despite his meteoric rise in popularity amid his love life, success on the field

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