Theta hat dot: upright and bold

I suggest you load both the upgreek (gulp...) and bm packages along with amsmath and write something along the lines of the code shown below.

\documentclass{article}
\usepackage{amsmath,upgreek,bm}
\begin{document}
$\dot{\bm{\hat{\uptheta}}}, 
 \dot{\hat{\uptheta}}, 
 \dot{\hat{\theta}}$
\end{document}

Stack a dot on top. The gap (currently .5pt) is adjustable with the optional argument to \stackon. EDITED to take Mico's advice (except with +/-1.3 mu instead of 1.5).

\documentclass{article}

\usepackage{mathtools}
\usepackage{scalerel,stackengine}
\stackMath

\newsavebox{\foobox}
\newcommand{\slantbox}[2][0]{\mbox{%
    \sbox{\foobox}{#2}%
    \hskip\wd\foobox
    \pdfsave
    \pdfsetmatrix{1 0 #1 1}%
    \llap{\usebox{\foobox}}%
    \pdfrestore
}}
\newcommand\unslant[2][-.25]{%
    \mkern1.3mu%
    \ThisStyle{\slantbox[#1]{$\SavedStyle#2$}}%
    \mkern-1.3mu%
}
\newcommand{\utheta}{\mathord{\unslant\theta}}

\begin{document}
    $\boldsymbol{\hat{\utheta}}$
and this
    $\stackon[.5pt]{\boldsymbol{\hat{\utheta}}}{.}$
\end{document}

\documentclass{article}

\usepackage{mathtools,bm}
\usepackage{scalerel}

\newsavebox{\foobox}
\newcommand{\slantbox}[2][0]{\mbox{%
    \sbox{\foobox}{#2}%
    \hskip\wd\foobox
    \pdfsave
    \pdfsetmatrix{1 0 #1 1}%
    \llap{\usebox{\foobox}}%
    \pdfrestore
}}
\newcommand\unslant[2][-.25]{%
    \mkern1mu%
    \ThisStyle{\slantbox[#1]{$\SavedStyle#2$}}%
    \mkern-1mu%
}
\newcommand{\utheta}{\unslant\theta}

\begin{document}


    $\dot{\boldsymbol{\hat{{\utheta}}}}$ $\boldsymbol{\dot{\hat{{\utheta}}}}$
\end{document}