Will the OpenLayers Plugin be updated for QGIS3?

In QGIS 3 use the XYZ Tiles in Data Browser

use

http://mt0.google.com/vt/lyrs=y&hl=en&x={x}&y={y}&z={z}&s=Ga

12th March 2018 update

There is a python script that will load in multiple xyz tiles available here https://raw.githubusercontent.com/klakar/QGIS_resources/master/collections/Geosupportsystem/python/qgis_basemaps.py (full credit is to Klas Karlsson https://twitter.com/klaskarlsson/status/972757121933733889)

Qgis 3 has a new plugin architecture so plugins are not immediately compatible with this new version. From the source repository it seems they wait for the official release of QGIS 3 to produce a new version of the plugin.

Beside this you have now the option to use XYZ Tile source to declare some slippy maps. for example you can use http://tile.openstreetmap.org/{z}/{x}/{y}.png for openstreetmap.

You'll find a bunch of resources in https://qms.nextgis.com (look for TMS)

The QuickMapServices (or QMS) Plugin makes it very easy to add basemaps from many different sources to your QGIS 3 project.

By default you get quite a few basemaps, but you can add hundreds of additional user-contributed basemaps by going to QuickMapServices --> Settings --> More Services --> Get Contributed Pack

Use the Search QMS tool to quickly locate basemaps.