So, is the transition from VD16 to VD17 smooth or continuous? The answer is: smooth.
Figure 1: Editions recorded in VD16 and VD17, 1590-1610 (total and by format)
VD17 seems to have caught up with VD16 enough that no discernible gap exists between the two. Here is the graph of total editions (orange) and a breakdown by format (folios, quartos, and octavos are blue, grey, and orange, respectively). Between 1600 and 1601, nothing interesting happens. (The jump in total editions in 1602 that isn't reflected in the individual formats is based primarily on a rise in duodecimo editions and editions without format data, by the way.)
An earlier look at the transition of incunable editions printed in Germany (as recorded in ISTC and GW) to early sixteenth-century editions in VD16 also found no gap.