"If Hearts and Rangers really are keen, I would consider any offer they made seriously," Miller told the Scottish News of the World.
"I'm free to speak to any interested club in January.
"George Burley has done an amazing job at Tynecastle and Hearts could be in the Champions League next season as reigning champions of Scotland.
"The fact I used to play for Hibs does not really come into it.
"My mates have been on the phone to say you can't possibly sign for them - but I have been away from Hibs for a long time and better players than Kenny Miller have managed to play for city rivals and cross the divide in the past."
"I think every Rangers fan knows I didn't want to leave the club four years ago.
"I am no quitter and I believe I had something to offer Rangers.
"I had scored against Monaco in the Champions League and scored five in a game against St Mirren to equal the SPL record. I was still only 20 and learning at the time.
"But the club offered good money for me and I can understand why they felt they had to accept at the time.
"That's business and there's no way I would ever hold it against Alex McLeish or Rangers.
"At the time, it was made clear that I wasn't going to play regular first-team football and Rangers were good enough to be totally honest and up front with me.
"So I know I could return one day with my head held high and there are certainly no grudges about the way I was treated.
"Alex McLeish gave me a regular game for Hibs and I have the utmost respect for him.
"But, if my form dips and the goals dry up, I'm not daft enough to believe any big club is going to be interested in me."