Vulnerability to PROJ >= 6 and GDAL >= 3

rgdal and sp are being changed to handle upstream changes in PROJ and GDAL, see https://www.r-spatial.org/r/2020/03/17/wkt.html. I see errors in running revdep checks from the development versions of sp (github - rsbivand/sp) and rgdal (R-Forge), with GDAL 3.0.4 and PROJ 7.0.0 in the brownian.bridge.dyn example:

>      dbbmm <- brownian.bridge.dyn(object=data2, location.error=12, dimSize=125, ext=.45, 
+                                   time.step=2, margin=15)
Computational size: 5.2e+06
Error in .local(object, raster, location.error = location.error, ext = ext,  : 
  Higher x grid not large enough, consider extending the raster in that direction or enlarging the ext argument
In addition: Warning messages:
1: In proj4string(object) :
  CRS object has comment, which is lost in output
2: In showSRID(uprojargs, format = "PROJ", multiline = "NO") :
  Discarded datum Unknown based on WGS84 ellipsoid in CRS definition
3: In proj4string(x) : CRS object has comment, which is lost in output
4: In proj4string(x) : CRS object has comment, which is lost in output
5: In FUN(X[[i]], ...) : CRS object has comment, which is lost in output
> traceback()
10: .Call("dbbmm2", coordinates(object)[, 1], coordinates(object)[, 
        2], c(object@means, 0), (as.numeric(timestamps(object)) - 
        min(as.numeric(timestamps(object))))/60, location.error, 
        xFromCol(raster, 1:ncol(raster)), yFromRow(raster, nrow(raster):1), 
        time.step, 4, object@interest)
9: .local(object, raster, location.error = location.error, ext = ext, 
       ...)
8: brownian.bridge.dyn(object = object, raster = raster, location.error = location.error, 
       ext = ext, ...)
7: brownian.bridge.dyn(object = object, raster = raster, location.error = location.error, 
       ext = ext, ...)
6: brownian.bridge.dyn(object = object, raster = rst, location.error = location.error, 
       margin = margin, window.size = window.size, ext = ext, ...)
5: brownian.bridge.dyn(object = object, raster = rst, location.error = location.error, 
       margin = margin, window.size = window.size, ext = ext, ...)
4: brownian.bridge.dyn(object = object, raster = raster, location.error = location.error, 
       margin = margin, window.size = window.size, ext = ext, ...)
3: brownian.bridge.dyn(object = object, raster = raster, location.error = location.error, 
       margin = margin, window.size = window.size, ext = ext, ...)
2: brownian.bridge.dyn(object = data2, location.error = 12, dimSize = 125, 
       ext = 0.45, time.step = 2, margin = 15)
1: brownian.bridge.dyn(object = data2, location.error = 12, dimSize = 125, 
       ext = 0.45, time.step = 2, margin = 15)

Because I cannot debug inside these methods, I cannot be sure what is happening. rgdal will be submitted to CRAN fairly soon. There are also errors in the tests.