By the end of 2029, I think that:
Josh and Anna will have ten kids. They will either be done or have only one more left before their quiver is closed. Josh will have another scandal but Anna will continue to stay by his side. Mackynzie (who will be 20 at this point) will already be married off and they will be anxiously waiting for her to make them grandparents.
I see Jana married (hopefully it's because she falls in love but I could also see JB and Michelle pressuring her if they believe a Jana wedding is the only way to keep Counting On going). I could see her with a few kids.
John and Abbie I see having five kids. Her Hyperemesis Gravidarum might slow them down a bit (especially if this occurs in subsequent pregnancies), but I doubt it will stop them.
Jill and Derick maybe have another kid or two. Despite the complications she's had with her first two births, they opt for a home birth and once again have to be transferred to the hospital for an emergency C-section. He graduates law school but doesn't do much with his degree before deciding he wants to do something else with his life.
Jessa and Ben will have seven kids and will still have a few more to go before their quiver is closed. We still aren't certain on what Ben does for a living.
Jinger and Jeremy have another two kids before going on some sort of birth control. After finishing at the seminary school, Jeremy becomes a pastor and Jinger relishes in being the paster's wife. They continue to live in a big city (whether they stay in LA permanently or not, who knows) far away from Northwest Arkansas.
Joseph and Kendra will have nine kids and showing no signs of slowing down.
Josiah and Lauren will have four kids. They will still be married, even if unhappily so, because they are too wrapped up in the Kool-Aid to show that their Godly marriage didn't work out.
Joy and Austin will have five kids. They will spend most of their time working at the Family Camp or flipping houses.
Most, if not all of the Howlers will be married with a few kids. Most of them will still work on Jim Bob properties but some will be forced to look for employment elsewhere.
A couple of the Lost Girls will be married. Another one will be unmarried and on her way to either becoming the next Jana or getting the hell out of this mess. Josie will not be married yet but when she does, her wedding will be super extravagant and way nicer than her siblings, which could lead to more resentment.
Jim Bob and Michelle will cling on to the TTH and any fam they still have for dear life. They will need a chart to remember all of their grandkids' names.