# EKF state propagation model using variables that are not part of state vector

I am trying to understand the EKF theory. Can the state transition function depend on variables that are not part of the state space? For example, the state propagation below depends on the quaternions that keep changing. If I get the quaternions from a very dependable source and I dont want to filter them, can I take them out of the state space? In that case, when calculating the Jacobian I will treat the quaternions as constants even though its a dynamic value from some external sensor. What are the implications of this approach? $$\begin{bmatrix} x\\ y\\ z\\ \end{bmatrix}_{k+1} = \begin{bmatrix} x\\ y\\ z\\ \end{bmatrix}_{k} + \begin{bmatrix} Rotation Matrix\\ using\\ Quaternions \end{bmatrix} * \begin{bmatrix} u \\ v \\ w \\ \end{bmatrix}_{k}$$

The state space I am using is $$\begin{bmatrix} x& y& z& u& v& w \end{bmatrix}^T$$ where x y z are the position coordinates and u v w are the linear velocities.