It will be interesting to see if he does attend. Very little is being shared, and for a reason, I think. The reason may be very private. We know Doria is attending but the failure to confirm Tom Sr may be rooted in issues that are associated with age and what not, not just a limp or physical health, ya know what I mean? Who knows. Whatever takes place will be for the best of everyone.
I know people are rooting for Doria to be the person to walk Meghan down the aisle

However, I question whether Doria would be willing/comfortable being front-and-center in that way at an event that is so public. I don't know her, of course. She may be fine doing so but her doing so would draw intense focus on the absent father, whereas there is another option. Given the symbolism of that walk, I would be intrigued if Harry and Meghan did something really outside-the-lines, like walked down the aisle together themselves. After all, that is the 'truth' of their relationship: Meghan's father (or mother) is not 'giving her away'. Harry and Meghan are very much giving each other to the other.
If they don't do the above I am partial to the idea of Prince Charles walking her down the aisle. It's been done before to show support of a controversial royal bride, not that Meghan is that at all, just it would be an amazing gesture of support towards Meghan (and Harry) given the complexity of the situation. JMO.