Maybe I'm generalizing this, but, I think it depends on the person. For me, the foot and tickle fetish go hand in hand. My foot fetish came long before my tickle fetish, as I have loved female feet since my age of reason, and I have only been into tickling since 1997.
That having been said, I have talked to people on this forum, especially girls, during my eight years here, where the girl in question who I was talking to, hated feet, talking about female feet, or her own feet, and wanted to discuss tickling only. Due to these experiences, and for this reason, I have concluded that the idea of a foot and tickling fetish going hand in hand, falls into the "Not necessarially" category. I know there are many tickle fetishists, like myself, who also have foot fetishes, but I also have talked to, and known, people who have tickle fetishes, who hate feet.
Maybe others have a different view than me, but this is just my experience. After eight years on the forum, I think I've had pretty extensive exposure to foot and tickle fetishists, to base my viewpoint on.
Mitch