Sony's tactic is to release new products not at once but in certain periods. For example now A7RIV, in 1 week A6900, in 3 months A7SIII, in 5 months 2 lenses, in 8 months A9 II etc... This way they can keep the attention by distributing new releases throughout the year.Canon said they would be the most aggressive camera company in terms of mirror-less development, but Sony certainly isn't taking a wait and see mode. Hopefully the new Canon RF models will be sooner than 2020
Canon and Nikon mostly release/announce 1-2 bodies together with some lenses so their releases are like a flash in a year.