In nearly every spectrum that is measurable, the sun's output is declining, with intermittent bursts of activity that are quite violent. How all this will conclude and in what way is unknowable except to say that the sun is absolutely entering a Grand Minimum.
The magnetic shield will become unstable, oscillate and then undergo massive drift or reversal. When exactly that happens, nobody knows for sure. Just the side effects from such events will stir the characteristic volcanism and tectonic activity that normally accompanies ice ages throughout the geological record.