How increased temperature (thermal vibrations and typical change in lattice parameter) would be expected to alter the diffraction pattern generally?

When there is a change in lattice parameter, thermal vibrations, and increased temperature, there are the chances that material is gone through any heat treatment or annealing or may be due to any other reason.

As the effect of that, the material structure will change, and diffraction patterns will also get changed. It will result in shifting of peaks or maybe the removal of some of the peaks and change in diffraction angles. As temperature shows different effects on every other atom, so this effect can be concluded in general only.