Well, I'm currently sort of tandem nursing, and plan/hope to continue after baby is born.
My 4 yo actually hasn't asked to nurse the last couple of nights. I'm kind of hoping I didn't inadvertently miss his last nursing session.
I'd like to get one last bf picture.
My 2 yo is nursing a LOT less than his brothers did at this age (and I was pg for each of them at this time, too). Sometimes he'll nurse 1 or 2 times in a day, but he'll go a whole day without nursing, too. I was really upset about it, but I think I've come to terms with the possibility that he'll wean. However, I think he'll pick up to nurse more once the baby is here. For awhile, if he saw me nursing his older brother, that is when he would want to nurse the most.
With each new baby, I have experienced the toddler wanting to nurse a lot more often. But, they've also been pretty good about waiting their turn to nurse, and realize baby gets to nurse first because they can eat big food and the baby can't. I try to have books on hand to read to the toddler while nursing the baby. If I absolutely have to, I'll nurse both at once, but I don't like it in general. Sometimes, though, it is an invaluable parenting tool and the only way I can get them both to sleep at the same time. Nursing the toddler is a way to reassure him that he's still my baby, too, and I think it has really cut down on jealousy issues.
Overall, the positives of tandem nursing have outweighed the negatives. My boys are all SOOO close. I am amazed at how well they play together and how much they show their love for one another. Of course, they fight and can be mean to one another, too... but I grew up with two fighting brothers close in age, and the difference in degree is pretty significant.