Yes, you can.
That seems to be the basic reason those themes exist: to give a class like Druid some perks, but especially to give them the theme's level 10 ability to access all their powers, all the time.
The detail of why it works that way
I'll be quoting the Werewolf powers in this answer. The Werebear and Wererat have identically worded powers, except for being bears and dire rats rather than wolves.
Beast Form: An effect type. A character can use a beast form power only while in beast form. Only certain characters can assume a beast form.
A Druid can cast their beast form powers from any beast form. There is nothing saying they can only cast those powers from their Wild Shape. They have their Wild Shape because they need a beast form to get at all their beast form powers - otherwise they would be a pretty silly class!
The Werebear/rat/wolf themes each come with a shape-changing power almost identical to the Druid's Wild Shape, except they're encounter powers rather than at-will:
Effect: You change from your humanoid form to a beast form — a wolf — that lasts until the end of the encounter. Alternatively, you can end the form as a minor action and shift 1 square. While you are in beast form, you can’t use weapon or implement attack powers that lack the beast form keyword, although you can sustain such powers.
This is a beast form, so now you can use beast form powers, except it prohibits you from using non-beast form powers! Note that using non-beast form powers is only prohibited by the power - it is not an inherent part of being in a beast form. At level 10, this limitation is removed:
Werewolf Level 10 Feature (10th level): When you use the wolf shape power, you can assume the form of a humanoid-wolf hybrid, instead of a wolf. While in hybrid form, your equipment does not become part of your new form, and you are not forced to drop any items you are holding. You are also not limited to using implement and weapon attack powers that have the beast form keyword.
That effectively reduces the first paragraph of the Wolf Shape power to this:
Effect: You change from your humanoid form to a beast form — a wolf — that lasts until the end of the encounter. Alternatively, you can end the form as a minor action and shift 1 square.
Hey, there's no more limitation on powers without the beast form keyword now! You've reached the apex of your theme, and now you can be a humanoid wolf, dire rat or bear, and have access to powers both with and without the beast form keyword!
A pity it doesn't also apply to your Wild Shape.