Is it possible to make a curly brace end in an arrow?

One way is to redefine decoration with this option in place or you can nest decorations with an arrowhead added as a markings decoration.

    % with \usetikzlibrary{decorations.markings} in the preamble
    \draw[postaction=decorate,
         decoration={markings,mark=at position 1 with {\arrow[blue]{>}}}
         ]
          decorate[decoration={brace,amplitude=10pt}]{ (0,0.7) to (10,0.7)};

You can also butcher the existing decoration and cancel the last curvy part

\pgfdeclaredecoration{half brace}{brace}
{%
  \state{brace}[width=+\pgfdecoratedremainingdistance,next state=final]
  {%
    \pgfpathmoveto{\pgfpointorigin}%
    \pgfpathcurveto%
    {\pgfqpoint{.15\pgfdecorationsegmentamplitude}{.3\pgfdecorationsegmentamplitude}}%
    {\pgfqpoint{.5\pgfdecorationsegmentamplitude}{.5\pgfdecorationsegmentamplitude}}%
    {\pgfqpoint{\pgfdecorationsegmentamplitude}{.5\pgfdecorationsegmentamplitude}}%
    {%
      \pgftransformxshift{+\pgfdecorationsegmentaspect\pgfdecoratedremainingdistance}%
      \pgfpathlineto{\pgfqpoint{-\pgfdecorationsegmentamplitude}{.5\pgfdecorationsegmentamplitude}}%
      \pgfpathcurveto%
      {\pgfqpoint{-.5\pgfdecorationsegmentamplitude}{.5\pgfdecorationsegmentamplitude}}%
      {\pgfqpoint{-.15\pgfdecorationsegmentamplitude}{.7\pgfdecorationsegmentamplitude}}%
      {\pgfqpoint{0\pgfdecorationsegmentamplitude}{1\pgfdecorationsegmentamplitude}}%
      \pgfpathcurveto%
      {\pgfqpoint{.15\pgfdecorationsegmentamplitude}{.7\pgfdecorationsegmentamplitude}}%
      {\pgfqpoint{.5\pgfdecorationsegmentamplitude}{.5\pgfdecorationsegmentamplitude}}%
      {\pgfqpoint{\pgfdecorationsegmentamplitude}{.5\pgfdecorationsegmentamplitude}}%
    }%
    {%
      \pgftransformxshift{+\pgfdecoratedremainingdistance}%
      \pgfpathlineto{\pgfqpoint{0pt}{.5\pgfdecorationsegmentamplitude}}%
    }%
  }%
  \state{final}{}%
}

If you place it in your preamble you can use it with half brace just as you would use regular brace

\begin{tikzpicture}
        \draw [decorate,decoration={half brace,amplitude=10pt}] (0,0.7) to (10,0.7);
\end{tikzpicture}

A dirty way to straighten out the end.

\documentclass[a4paper,12pt]{article}
\usepackage{tikz,tikz-cd}
\usetikzlibrary{decorations.pathreplacing}
\pagestyle{empty}

\begin{document}
    \begin{center}
        \begin{tikzpicture}
        \draw [->] (0,0) -- (10,0);
        \draw (0,0.2) -- (0,-0.2);
        \draw (1.5,0.2) -- (1.5,-0.2);
        \draw (3,0.2) -- (3,-0.2);
        \draw (4.5,0.2) -- (4.5,-0.2);
        \node [below] at (0,-0.2) {0};
        \node [below] at (1.5,-0.2) {1};
        \node [below] at (3,-0.2) {2};
        \node [below] at (4.5,-0.2) {3};
        \node [above] at (1.6,0.2) {\$1500};
        \node [above] at (3,0.2) {\$1500};
        \node [above] at (4.5,0.2) {\$1500};
        \begin{scope}
        \clip(9, 1.5) rectangle (-1, -0.5);
        \draw [decorate,decoration={brace,amplitude=10pt}] (0,0.7) to (10,0.7);
        \end{scope}
        \draw[->] ([yshift=5pt]9, 0.7) -- ([yshift=5pt]10,0.7);
        \node at (5,1.2) {simple ordinary annuity};
        \node at (4,1.8) {$j_1=6\%$};
        \end{tikzpicture}
    \end{center}
\end{document} 

which produces:

Is this what you want?

Along the lines of percusse's answer, you could do something like

\documentclass{article}  
\usepackage{tikz}
\usetikzlibrary{decorations.markings,decorations.pathreplacing}

\begin{document}
\begin{tikzpicture}
\begin{scope}
\clip (0,0.0) rectangle(9.5,2.0);
\draw [decorate,decoration={brace,amplitude=10pt}] (0,0.7) to (10,0.7);
\end{scope}
\path[postaction=decorate,decoration={markings,mark=at position 0.95 with {\arrow{>}}}] decorate[decoration={brace,amplitude=10pt}] { (0,0.7) to (10,0.7)};
\end{tikzpicture}
\end{document}